1. Field of the Invention
The present invention relates to an ink jet printer head in which a spacer for setting a cover member and a nozzle plate with nozzle openings fixed distance apart and having pressure generating chambers, reservoirs, and ink supply paths connecting them, is formed of a silicon single-crystal substrate.
2. Related Art
An ink jet printer head shoots forth ink droplets onto a recording medium to form dots thereon. Print of extremely high resolution is realized if the size of the ink droplets is reduced. For high speed printing, the number of nozzle openings must be increased. Particularly, in the printer head of the type in which piezoelectric vibrating elements are used as an energy source for expelling ink droplets, the pressure generating chamber must be designed to be as large as possible in order to efficiently use the energy of the piezoelectric vibrating element. This requirement for the efficient use of the energy vis-a-vis a large pressure generating chamber is contradictory to the current tendency to reduce the size of the printer head.
One measure currently taken to help solve this contradictory problem is to reduce the thickness of the wall partitions the adjacent pressure generating chambers, and to enlarge the pressure generating chambers in the longitudinal direction.
To form the pressure generating chambers and the reservoirs, path holes are formed in the spacer that is used for setting the vibrator plate and the nozzle plate a fixed distance apart. Since the path holes must be formed in conformity with the pressure generating chambers, and since the latter are extremely small and complicatedly shaped, the etching technique is usually used.
A photosensitive resin film is usually used for the spacer. A spacer made of photosensitive resin has, however, low mechanical strength. A printer head using such a defective spacer suffers from cross talk, deflection, and the like, and so this approach to achieving high resolution is accompanied by deterioration of print quality.
To cope with this problem, proposals are in U.S. Pat. No. 4,312,008 and Examined Japanese Patent Publication No. Sho. 58-40509. In these proposals, a silicon single-crystal substrate vertically oriented in (110) is cut out so as to have the thickness suitable for a spacer. Path holes, shaped for pressure generating chambers, and ink supply paths are formed in the silicon single-crystal substrate by an anisotropic etching process. The spacer of the silicon single-crystal substrate has a large mechanical strength. Therefore, the deflection of the whole print head, which is caused by deformation of the piezoelectric vibrating elements, is minimized. The walls that undergo the anisotropic etching process are substantially vertical with respect to the surface of the spacer. Because of this, the pressure generating chambers can be uniformly formed.
This spacer has the following problem, however. The walls that undergo the anisotropic etching process are limited in their directions by the crystal face orientation. Therefore, it is difficult to shape the pressure generating chambers so as to be ideal for the ink jet printer head. Because of the unsatisfactorily shaped pressure generating chambers, ink tends to stay and to generate bubbles in the pressure generating chambers.
The spacer formed of the silicon single-crystal substrate is advantageous in that the pressure generating chambers may be reduced in size, but is disadvantageous in that a mechanical strength of the whole spacer is small. Because of the fragile spacer, it is difficult to handle the spacers in assembling the ink jet printer head. Further, it is difficult to secure a compliance sufficient for effectively utilizing the pressure energy generated by the piezoelectric vibrating elements and the heat generating means.